Printing apparatus and a method for changing power modes

ABSTRACT

A communication apparatus communicating with an external apparatus via a relaying device is provided. The communication apparatus includes a communication unit configured to perform communication with the relaying device, and a control unit configured to reduce a communication speed of the communication unit to a lower speed if the communication apparatus is to be shifted from a first power mode to a second power mode in which power consumption is lower than that in the first power mode. The communication unit, if the communication apparatus shifts to the second power mode, transmits identification information of the communication apparatus to the relaying device using a first method, and after a predetermined time has passed, transmits the identification information to the relaying device by a second method.

RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.14/883,022 filed on Oct. 14, 2015, which is a Continuation of U.S.patent application Ser. No. 13/893,063, filed May 13, 2013, now U.S.Pat. No. 9,197,571, which claims the benefit of Japanese Application No.2012-111863 filed May 15, 2012, which are hereby incorporated byreference herein in their entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a communication apparatus forcommunicating with a relaying device in a network.

Description of the Related Art

A network interface card (NIC) has conventionally been used for enablinga digital multi-function peripheral that performs printing,transmission, and the like to communicate with other devices via anetwork such as a local area network (LAN).

Ethernet is popular as a representative network standard. A NICcompliant with the Ethernet standard can perform communication byselecting one of communication speeds of 10 Mbps, 100 Mbps, and 1000Mbps.

Recently, power saving has been required of the digital multi-functionperipherals. In this regard, for example, Japanese Laid-Open PatentApplication No. 2001-154763 discusses a technique for saving power byreducing a communication speed of an NIC when the digital multi-functionperipheral operates in a power-saving mode.

To achieve more power saving, in addition to the reduction in thecommunication speed as discussed in Japanese Laid-Open PatentApplication No. 2001-154763, Japanese Laid-Open Patent Application No.2007-276341 discusses a technique for cutting off power supply to a partof a communication apparatus when the communication apparatus operatesin a power-saving mode.

As a recent network related technique, virtual local area network (VLAN)has been popular. The VLAN technique virtually divides a plurality ofphysically connected computer terminals on a network into a plurality ofgroups (“virtual networks”) by using a relaying device such as aswitching hub to manage the groups as if they belong to different LANsrespectively. The VLAN technique is further classified into a staticVLAN technique and a dynamic VLAN technique. In the static VLANtechnique, computer terminals are divided into a plurality of groups foreach port of a switching hub. In the dynamic VLAN technique, a switchinghub virtually divides a plurality of computer terminals into a pluralityof groups to manage the terminals based on information (for example,media access control or MAC address) acquired from each computerterminal connected to a port.

It is assumed that a communication link with a switching hub is cut off(“linked-down”) in a communication apparatus connected to the switchinghub compliant with the dynamic VLAN technique. In such a case, toreconnect (“link-up”) the communication link with the switching hub, thecommunication apparatus has to retransmit information such as a MACaddress to the switching hub. This is because the switching hubsupporting the dynamic VLAN technique considers that the computerterminal whose communication link has been cut off no longer belongs to(“participates in”) the VLAN by cutting-off of the communication link.To participate in the VLAN including the switching hub, as discussed inJapanese Laid-Open Patent Application No. 2009-278240, the communicationapparatus has to transmit information such as a MAC address to theswitching hub.

SUMMARY OF THE INVENTION

The present invention is directed to secure transmission of informationnecessary for a communication apparatus to participate in a virtualnetwork, to a switching hub while achieving power saving of thecommunication apparatus.

According to an aspect of the present invention, a communicationapparatus communicating with an external apparatus via a relaying deviceis provided. The communication apparatus includes a communication unitconfigured to perform communication with the relaying device, and acontrol unit configured to reduce a communication speed of thecommunication unit to a lower speed if the communication apparatus is tobe shifted from a first power mode to a second power mode in which powerconsumption is lower than that in the first power mode. Thecommunication unit, if the communication apparatus shifts to the secondpower mode, transmits identification information of the communicationapparatus to the relaying device using a first method, and after apredetermined time has passed, transmits the identification informationto the relaying device by a second method.

According to the present invention, participation of a communicationapparatus in a network can be secured while achieving power saving ofthe communication apparatus.

Further features and aspects of the present invention will becomeapparent from the following detailed description of exemplaryembodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate exemplary embodiments, features,and aspects of the invention and, together with the description, serveto explain the principles of the invention.

FIG. 1 is a block diagram illustrating an overall configuration of acommunication system.

FIG. 2 is a block diagram illustrating a configuration of amultifunction peripheral (MFP).

FIG. 3 is a block diagram illustrating a configuration of a controlunit.

FIG. 4 illustrates a software configuration of a program executed by amain central processing unit (CPU).

FIG. 5 is a block diagram illustrating a configuration of a switchinghub.

FIG. 6 illustrates a database managed in the switching hub configuring aVLAN.

FIG. 7 is a flowchart illustrating an operation performed by a CPU ofthe control unit.

FIG. 8 is a flowchart illustrating an operation performed by a CPU of anetwork unit.

FIG. 9 illustrates a VLAN database in a subnet based VLAN.

FIG. 10 illustrates a VLAN database in a user based VLAN.

DESCRIPTION OF THE EMBODIMENTS

Various exemplary embodiments, features, and aspects of the inventionwill be described in detail below with reference to the drawings.

Components of the exemplary embodiments are only examples, and the scopeof the present invention is not limited to the examples.

FIG. 1 is a block diagram illustrating a configuration of acommunication system including a communication apparatus according tothe first exemplary embodiment of the present invention.

The communication system in FIG. 1 includes a digital MFP (hereinafter,simply referred to as MFP) 1003, and personal computers (PCs) 1001 and1002 serving as external apparatuses. The MFP 1003 is provided with aplurality of functions such as a network print function, and a networktransmission function. The PCs 1001 and 1002 and the MFP 1003 areconnected to a LAN 1005 via a switching hub 1004.

The MFP 1003 includes an operation unit 1010, a scanner unit 1008, and aprinter unit 1007. The operation unit 1010 is used when a user performsvarious kinds of operations. The scanner unit 1008 reads imageinformation according to an instruction from the operation unit 1010.The printer unit 1007 prints image data on a sheet. The MFP 1003 furtherincludes a control unit 1006 that controls the scanner unit 1008 and theprinter unit 1007 according to an instruction from the operation unit1010, or a remote instruction from the PC 1002.

The PCs 1001 and 1002 can transmit a print job including image data ofone page or a plurality of pages to the MFP 1003 via the LAN 1005. ThePCs 1001 and 1002 can transmit, other than print jobs, various kinds ofcommands to the MFP 1003. The PCs 1001 and 1002 can transmit a print jobto MFPs connected to the LAN 1005 other than the MFP 1003.

FIG. 2 is a block diagram illustrating a configuration of the MFP 1003illustrated in FIG. 1.

In FIG. 2, the scanner unit 1008 includes a platen glass 101 for placinga document thereon, and an automatic document feeder 142 forsequentially feeding documents to a predetermined position of the platenglass 101. The scanner unit 1008 scans the document placed on the platenglass 101 in a main scanning direction during an exposure process. Thescanner unit 1008 includes a document illumination lamp 102, a scanningmirror 103, a scanning unit 147 disposed below the platen glass 101, andscanning mirrors 104 and 105 for deflecting reflected light of thescanning mirror 103 toward a charge coupled device (CCD) unit 106. Thescanner unit 1008 further includes a scanning unit 148 for scanning in asub-scanning direction at a half speed of the scanning unit 147, and animaging lens 107 for receiving the reflected light of the scanningmirror 105 and forming an image. The CCD unit 106 is provided with animage sensor 108 consisting of a CCD for converting the formed imageinto a digital image signal of, for example, 8 bits, and a CCD driver109 for driving the image sensor 108.

The control unit 1006 receives an instruction from the operation unit1010 and generates image data based on the image signal output from theimage sensor 1008, and controls the entire apparatus. With reference toFIG. 3, the control unit 1006 will be described in detail below.

The printer unit 1007 exposes a photosensitive drum 110 to light to forman electrostatic latent image based on image data generated in thecontrol unit 1006. The printer unit 1007 includes, for example, anexposure unit 117 consisting of a semiconductor laser, and a developmentunit 118 containing toner that is black developer. The printer unit 1007develops the electrostatic latent image on the photosensitive drum 110with the toner. The printer unit 1007 further includes a pre-transfercharging device 119 for applying high voltage to the toner imagedeveloped on the photosensitive drum 110 prior to transfer.

The printer unit 1007 further includes a manual feed tray 120, and sheetfeeding units 122, 124, 142, and 144 for storing sheets. The printerunit 1007 further includes feeding rollers 121, 123, 125, 143, and 145for feeding sheets on the manual feed tray 120 or stored in the sheetfeeding units 122, 124, 142, and 144, respectively. The printer unit1007 further includes registration rollers 126 for feeding the sheet(s)fed from the sheet feeding rollers 121, 123, 125, 143, or 145 to thephotosensitive drum 110. The feeding rollers 121, 123, 125, 143, and 145feed and stop the sheet(s) on the manual feed tray 120 or the sheet(s)stored in the sheet feeding units 122, 124, 142, and 144 at the positionof the registration rollers 126. The feeding rollers 121, 123, 125, 143,and 145 feed the sheet(s) in synchronization with write timing of thetoner image developed on the photosensitive drum 110.

The printer unit 1007 further includes a transfer charger 127 fortransferring the toner image developed on the photosensitive drum 110 tothe fed sheet, and a separation charger 128 for separating, from thephotosensitive drum 110, the sheet on which the toner image has beentransferred from the photosensitive drum 110. The printer unit 1007includes a conveyance belt 129 for conveying the separated sheet to afixing device 130 described below, and a cleaner 111 for recoveringtoner remaining on the photosensitive drum 110 without transferred. Theprinter unit 1007 includes a pre-exposure lamp 112 for discharging thephotosensitive drum, and a primary charging unit 113 for uniformlycharging the photosensitive drum 110.

The printer unit 1007 includes a fixing device 130 for fixing the tonerimage on the sheet on which the toner image has been transferred, and asorter 132 for receiving the sheet on which the toner image is fixed viaa flapper 131. The printer unit 1007 includes an intermediate tray 137for receiving the sheet on which the toner image is fixed via theflapper 131 and feed rollers 133 to 136. The printer unit 1007 includesa re-feed roller 138 for feeding the sheet on the intermediate tray 137to the photosensitive drum 110 again. The flapper 131 switches thefeeding destination of the sheet on which the toner image is fixed,between the sorter 132 and the intermediate tray 137. The feed rollers133 to 136 are configurable both not to invert (i.e., formultiple-printing) and to invert (i.e., for two-sided printing) thesheet on which the toner image is fixed.

FIG. 3 is a block diagram illustrating a configuration of the controlunit 1006 in FIG. 2.

In FIG. 3, the control unit 1006 is connected to the scanner unit 1008,the printer unit 1007, the switching hub 1004, and a public line toinput and output image data or device information.

The control unit 1006 includes a raster image processor (RIP) 2010 forrasterizing a page description language (PDL) code included in a printjob received from a computer terminal on the LAN via the LAN 1005 to bea bitmap image. The control unit 1006 includes a scanner imageprocessing unit 2011 for correcting, processing, or editing image datainput from the scanner unit 1008. The control unit 1006 further includesa printer image processing unit 2012 for correcting or changing theresolution of the image data output (printed) from the printer unit1007, and an image rotation unit 2013 for rotating the image data.

The control unit 1006 includes an image compression unit 2014 forcompressing or decompressing multivalued image data in a JointPhotographic Experts Group (JPEG) format, and compressing ordecompressing binary image data in a Joint Bi-level Image Experts Group(JBIG) format, a Modified Modified READ (MMR) format, or a ModifiedHuffman (MH) format. The control unit 1006 includes a device interface(I/F) 2015 for connecting the control unit 1006 to the scanner unit 1008and the printer unit 1007 to perform synchronous/asynchronous conversionof image data. The control unit 1006 further includes an image bus 2018for interconnecting these components to transfer image data at a highspeed.

The control unit 1006 includes a CPU 2001 for controlling the MFP 1003.Hereinafter, the CPU 2001 of the control unit 1006 is referred to as“main CPU” to distinguish the CPU 2001 from a CPU of a network unit 2008described below. The CPU 3001 in the network unit 2008 described belowis referred to as “sub CPU”.

The control unit 1006 includes a random access memory (RAM) 2006 servingas a system work memory for operating the main CPU 2001. The RAM 2006also serves as an image memory for temporarily storing image data. Thecontrol unit 1006 includes an operation unit I/F 2007 for outputting, tothe operation unit 1010, image data to be displayed on the operationunit 1010.

The operation unit I/F 2007 transmits information entered by a user ofthe system via the operation unit 1010 to the main CPU 2001. The controlunit 1006 includes a network unit 2008 connected to the LAN 1005 via theswitching hub 1004 to communicate (transmit or receive) with the PC 1002or a computer terminal (for example, PC 1001) on the LAN 1005. Thecontrol unit 1006 includes a modem unit 2009 connected to a public lineto communicate (transmit or receive) data with an external facsimiledevice. The network unit 2008 receives data from the computer terminalon the LAN 1005, and processes the received data. The control unit 1006includes a read-only memory (ROM) 2002 for storing a boot program to beexecuted by the main CPU 2001, and a hard disk drive (HDD) 2003 forstoring system software, image data, or a software count value. Thecontrol unit 1006 includes a scanner/printer communication I/F 2005 forcommunication with CPUs in the scanner unit 1008 and the printer unit1007, and a system bus 2017 for interconnecting these components.

The control unit 1006 includes an image bus I/F 2004 serving as a busbridge for interconnecting the system bus 2017 and the image bus 2018 toconvert a data structure. The control unit 1006 includes a power OFF/ONunit 2016 for supplying direct current (DC) power received from thepower supply unit 1009 via a power supply line 2019, to predeterminedcircuit elements of the control unit 1006 via power supply lines 2020and 2021. The power OFF/ON unit 2016 is controlled according to acontrol signal received from the network unit 2008 via a control signalline 2023 and a control signal received from the main CPU 2001 via acontrol signal line 2022. The power OFF/ON unit 2016 selectively turnson or off the power supply lines 2020 and 2021. The power supply line2020 is connected to the main CPU 2001, the ROM 2002, the HDD 2003, theimage bus I/F 2004, and the scanner/printer communication I/F 2005. Thepower supply line 2020 is connected to the device I/F 2015, the imagerotation unit 2013, the image compression unit 2014, the RIP 2010, thescanner image processing unit 2011, and the printer image processingunit 2012. The power supply line 2021 is connected to the RAM 2006, theoperation I/F 2007, the network unit 2008, and the modem unit 2009.

The MFP 1003 in FIG. 1 performs printing processing as follows based ona print job transmitted from a computer terminal (PC 1001, PC 1002, orthe like) connected to the LAN 1005. The main CPU 2001 stores in the RAM2006 print data, which is image data, received from the computerterminal connected to the LAN 1005 via the network unit 2008. The mainCPU 2001 supplies the image data to the RIP 2010 via the image bus I/F2004. The RIP 2010 expands the image data (PDL code) in bitmap data. Theimage compression unit 2014 compresses the image data to store the datain the HDD 2003. The image data (compressed bitmap data) stored in theHDD 2003 is supplied to the image compression unit 2014 via the imagebus I/F 2004. The image compression unit 2014 decompresses the suppliedimage data (compressed bitmap data). The printer image processing unit2012 performs correction and resolution-conversion of the printer imagedata. The image rotation unit 2013 rotates the image data if necessary.The variously processed image data is transmitted as print data to theprinter unit 1007 via the device I/F 2015. The printer unit 1007performs print processing on the sheet.

The MFP 1003 is operable in a deep sleep mode that is one ofpower-saving modes. In a normal mode, the power supply unit 1009supplies power to the power OFF/ON unit 2016 via the power supply line2019. The main CPU 2001 controls the power OFF/ON unit 2016 such thateach of the power supply line 2020 and the power supply line 2021 isturned on. In such a state, the power supply unit 1009 supplies power toboth of the main CPU 2001 and the network unit 2008.

In the deep sleep mode, the power supply unit 1009 supplies power to thepower OFF/ON unit 2016 via the power supply line 2019. The main CPU 2001controls the power OFF/ON unit 2016 such that the power supply line 2020is turned off and the power supply line 2021 is turned on. In such astate, power supplied to the main circuit components including the mainCPU 2001 of the control unit 1006 is cut off. Consequently, powerconsumption of the MFP 1003 can be largely reduced. When the networkunit 2008 receives data such as a print job from the computer terminalon the LAN 1005, the network unit 2008 can control the power OFF/ON unit2016 to return to the normal mode. In the deep sleep mode, the powersupplied to the main CPU 2001 is cut off; however, other arrangementscan be employed. For example, the clock frequency of the main CPU 2001can be reduced to lower than that in the normal mode to reduce the powerconsumption. Alternatively, without cutting off the power supply, thepower to be supplied can be reduced to lower than that in the normalmode. In an exemplary embodiment, in the deep sleep mode, the main CPU2001 can execute only limited processing compared to the normal mode.The limited processing includes at least processing of packets receivedfrom the computer terminal on the LAN 1005 by the network unit 2008.

In the deep sleep mode, power has been supplied to the RAM 2006 from thepower supply unit 1009. Consequently, the RAM 2006 performs aself-refreshing operation to back up a system program.

In the above description, the network unit 2008 switches the powersupply mode from the deep sleep mode to the normal mode. Alternatively,other arrangements can be employed. Specifically, instead of using thenetwork unit 2008, the modem unit 2009 or the operation unit I/F 2007can switch the mode from the deep sleep mode to the normal mode. Theformer case enables facsimile communication with the public line, andthe latter case enables reception of an instruction from the user of theoperation unit 1010.

The MFP 1003 in FIG. 1 returns from the deep sleep mode to the normalmode as described below.

For example, when the network unit 2008 receives a print job from the PC1002, the network unit 2008 analyzes to determine whether the packetsreceived as the print job include data sequence corresponding to aphysical address unique to the apparatus. If the network unit 2008detects the data sequence corresponding to the apparatus, the networkunit 2008 controls the power OFF/ON unit 2016 via the control signalline 2023 to turn the power supply line 2021 on, and starts the main CPU2001. The main CPU 2001 determines whether the start of the CPU 2001 iscaused by a return from the deep sleep mode to the normal mode, based onthe power OFF/ON unit 2016. If the main CPU 2001 determines that thestart is caused by a return from the deep sleep mode to the normal mode,the main CPU 2001 starts a boot sequence. In this processing, the mainCPU 2001 uses the system program backed up by the RAM 2006 at the timeof shift to the deep sleep mode, without performing a sequence fordown-loading the system program from the HDD 2003 to the RAM 2006. Bysuch processing, the control unit 1006 is set to the normal mode, andthe control unit 1006 instructs the printer unit 1007 to start printingin response to the print job from the computer terminal on the LAN 1005.

The network unit 2008 includes the sub CPU 3001 for controlling thenetwork unit 2008, a MAC/PHY unit 3002, a bus I/F 3003, a ROM 3004, anda RAM 3005, which are interconnected via a bus. The network unit 2008 isconnected to the system bus 2017 via the bus I/F 3003. The MAC/PHY unit3002 communicates with the switching hub 1004 to transmit and receivepacket data.

The ROM 3004 stores a wake-on-LAN pattern (WOL pattern) for returningfrom the deep sleep mode to the normal mode, and a proxy responsepattern for responding to a received packet without returning from thedeep sleep mode to the normal mode. Hereinafter, an operation performedwhen the MFP 1003 receives a packet of the WOL pattern to return the MFP1003 from the deep sleep mode to the normal mode is described.

First, an operation performed when the MAC/PHY unit 3002 receives apacket of the WOL pattern in the deep sleep mode is described. The subCPU 3001 determines, when the MFP 1003 operates in the deep sleep mode,whether a packet received by the MAC/PHY unit 3002 via the LAN 1005matches the WOL pattern stored in the ROM 3004. If the sub CPU 3001determines that the packet received by the MAC/PHY unit 3002 matches theWOL pattern, the sub CPU 3001 transmits an instruction for startingpower supply to the power OFF/ON unit 2016 via the control signal line2023. As a result, the power supply to the main CPU 2001 and othercomponents is resumed.

Next, an operation performed when the MAC/PHY unit 3002 receives apacket of the proxy response pattern in the deep sleep mode isdescribed. The ROM 3004 stores the proxy response pattern and responsedata associated with the proxy response pattern. The response dataincludes, for example, status information of the MFP 1003 (e.g.,information indicating an operation mode of the MFP 1003, informationindicating the remaining amount of sheets, and the like). The sub CPU3001 determines, when the MFP 1003 operates in the deep sleep mode,whether a packet received by the MAC/PHY unit 3002 via the LAN 1005matches the proxy response pattern stored in the ROM 3004. If the subCPU 3001 determines that the packet received by the MAC/PHY unit 3002matches the proxy response pattern, the sub CPU 3001 reads the responsedata corresponding to the matched proxy response pattern from the RAM3005. The sub CPU 3001 transmits the response data read from the RAM3005 to the computer terminal on the LAN 1005. The terminal is thetransmission source of the proxy response pattern. Even if the sub CPU3001 detects the proxy response pattern, the sub CPU 3001 issues noinstruction to the power supply unit 1009 for causing the power OFF/ONunit 2016 to resume the power supply to the main CPU 2001 and othercomponents via the power supply line 2020. Consequently, when the MFP1003 receives the proxy response pattern and performs the responseprocessing, the MFP 1003 can perform the response processing whilemaintaining the deep sleep mode without returning from the deep sleepmode to the normal mode.

The network unit 2008 can perform communication complying with Ethernetstandard. The network unit 2008 can perform communication in a pluralityof communication modes, and can communicate with the switching hub 1004,for example, at one of communication speeds of 10 Mbps, 100 Mbps, and1000 Mbps. The switching hub 1004 complies with the Ethernet standard,and can perform communication at one of communication speeds of 10 Mbps,100 Mbps, and 1000 Mbps.

FIG. 4 illustrates a software configuration of a program executed by themain CPU 2001. The program illustrated in FIG. 4 is stored in the HDD2003, and the main CPU 2001 executes a boot program to read out theprogram from the HDD 2003 to the RAM 2006.

In FIG. 4, an operating system (OS) 4000 operates as a basic program forexecuting various driver programs described below. A RAM control driver4001 is a program for controlling the RAM 2006 based on an instructionfrom the OS 4000. An operation unit I/F control driver 4002 is a programfor controlling the operation unit I/F 2007 based on an instruction fromthe OS 4000. A network unit control driver 4003 is a program forcontrolling the network unit 2008 based on an instruction from the OS4000. A modem unit control driver 4004 is a program for controlling themodem unit 2009 based on an instruction from the OS 4000. A scanner unitcontrol driver 4005 is a program for controlling the scanner unit 1008based on an instruction from the OS 4000. A printer unit control driver4006 is a program for controlling the printer unit 1007 based on aninstruction from the OS 4000.

The main CPU 2001 executes the OS 4000 read on the RAM 2006 to controlthe units including the RAM 2006, the operation unit I/F 2007, thenetwork unit 2008, the modem unit 2009, the printer unit 1007, and thescanner unit 1008. The programs 4001 to 4006 can operate in parallel onthe OS 4000. The main CPU 2001 executes the programs while switching theprograms in a time-division manner such that the programs 4001 to 4006can operate in parallel.

FIG. 5 is a block diagram illustrating a configuration of the switchinghub 1004.

The switching hub 1004 includes three connection ports of a first port5004, a second port 5005, and a third port 5006. The switching hub 1004includes a relay circuit 5003 for relaying data among the ports. Undercontrol of a CPU 5001, the relay circuit 5003 can switch connections tothe ports. A RAM 5002 stores a VLAN database illustrated in FIG. 6described below. The VLAN database is data associating, as describedbelow, identification information (in the exemplary embodiment, MACaddress) for identifying a computer terminal that can participate in avirtual network (VLAN) of the switching hub 1004, with a type of VLAN.The CPU 5001 determines whether information included in the packet datareceived from each port matches the identification information stored inthe VLAN database. If the CPU 5001 determines that the informationmatches the identification information, the CPU 5001 performs managementto cause the terminal that has transmitted the packet data toparticipate in the virtual network corresponding to the matchedidentification information.

The switching hub 1004 can configure a dynamic VLAN as a virtualnetwork. In the VLAN technique, a plurality of computer terminals on anetwork physically connected by using a relaying device such as aswitching hub is divided into a plurality of groups (virtual networks),and each group is managed to belong to different LANS.

The VLAN technique includes a technique for configuring a VLAN bygrouping a plurality of ports of the switching hub (static VLANtechnique). According to the technique, for example, the switching hubmanages two computer terminals connected to the first and second portsas terminals configuring a VLAN 1, and one computer terminal connectedto the third port as a terminal configuring a VLAN 2.

The VLAN technique also includes a dynamic VLAN technique. According tothe dynamic VLAN technique, the switching hub virtually divides aplurality of computer terminals into a plurality of groups to manage theterminals based on information acquired from each of computer terminalsconnected to the switching hub.

For example, in a case of a MAC based VLAN technique, MAC addresses areacquired from computer terminals connected to the switching hub, and theswitching hub performs management to determine to which VLAN a computerterminal with any MAC address belongs.

In a case of a subnet based VLAN technique, for example, IP addressesare acquired from computer terminals connected to the switching hub, andthe switching hub performs management to determine to which VLAN acomputer terminal with any IP address belongs.

In a case of a user based VLAN technique, for example, user informationis acquired from computer terminals connected to the switching hub, andthe switching hub performs management to determine to which VLAN acomputer terminal of any user information belongs.

In the description, it is assumed that the switching hub 1004illustrated in FIG. 1 complies with the MAC based VLAN.

In FIG. 1, the PC 1001, the PC 1002, and the MFP 1003 are connected tothe switching hub 1004. The PC 1001 is connected to the first port 5004of the switching hub. The PC 1002 is connected to the second port 5005.The MFP 1003 is connected to the third port 5006. The switching hub 1004performs management such that the PC 1002 belongs to a first VLAN (VLAN1), and the PC 1001 and the MFP 1003 belong to a second VLAN (VLAN 2).In this case, the VLAN database illustrated in FIG. 6 is stored in amemory (not illustrated) in the switching hub 1004.

In FIG. 6, the PC 1001 having a MAC address of 00:00:85:00:00:01 and theMFP 1003 having a MAC address of 00:00:85:00:00:03 are managed as theVLAN 1 by the switching hub. The PC 1002 having a MAC address of00:00:85:00:00:02 is managed as the VLAN 2.

When the switching hub 1004 is managed as illustrated in FIG. 6, even ifthe PC 1002 designates the IP address of the PC 1001 to request datatransmission or reception, the PCs 1002 and 1001 belong to differentVLANs. Consequently, no data is transmitted or received between the PCs1002 and 1001 as the terminals in the same LAN segment. Consequently,when the switching hub 1004 receives a broadcast packet from the PC1001, the switching hub 1004 transmits the broadcast packet to the MFP1003 that belongs to the same VLAN (VLAN 2) as the PC 1001. Meanwhile,the switching hub 1004 transmits no broadcast packet to the PC 1002 thatbelongs to a VLAN (VLAN 1) different from that of the PC 1001. In FIG.6, the PC 1001 having a MAC address of 00:00:85:00:00:01 is in a VLANnon-participation state. In the above description, however, it isassumed that the PC 1001 is in a participation state.

In the VLAN database in FIG. 6, the VLAN participation state is amanagement item for determining whether a computer terminal identifiedby a MAC address is participating in the VLAN, or not. As describedabove, to enable participation of a certain computer terminal in theVLAN, simple establishment of a communication link with the switchinghub 1004 is not enough. Namely, in the communication link establishedstate, the switching hub 1004 has to further receive a MAC address ofthe computer terminal. It is assumed that the switching hub 1004 hasreceived a MAC address of a computer terminal in a link-up state where acommunication link with the computer terminal has been established. Inthis case, the switching hub 1004 performs management to switch a VLANparticipation state corresponding to the MAC address fromnon-participation to participation. The MAC address, the VLAN number,and the participation state of the VLAN are managed in association witheach port (from the first port 5004 to the third port 5006) of theswitching hub 1004.

An operation performed by the MFP 1003 connected to the switching hub1004 supporting the MAC based VLAN will be described.

FIG. 7 is a flowchart illustrating an operation performed by the mainCPU 2001 of the control unit 1006. FIG. 8 is a flowchart illustrating anoperation performed by the sub CPU 3001 of the network unit 2008.

The operation in the flowchart in FIG. 7 is started by starting powersupply from the power supply unit 1009 to the main CPU 2001.

There follow two cases for starting power supply from the power supplyunit 1009 to the main CPU 2001. One is a case where a main switch (notillustrated) of the MFP 1003 is switched from off to on. The other is acase where the operation mode of the MFP 1003 is switched from the deepsleep mode to the normal mode in a state where the main switch of theMFP 1003 is in the on state.

In step S701, the main CPU 2001 reads the boot program stored in the ROM2002 to expand the program on the RAM 2006, and executes the bootprogram expanded on the RAM 2006. The main CPU 2001 reads, by executingthe boot program, the OS 4000 and various control drivers 4001 to 4006illustrated in FIG. 4 from the HDD 2003 to expand them on the RAM 2006.Then, the main CPU 2001 operates the OS 4000 expanded on the RAM 2006and the network unit control driver 4003 to be executed on the OS 4000to execute each step.

In step S702, the OS 4000 determines whether the MFP 1003 has returnedfrom the deep sleep mode to the normal mode, or whether the main switchhas been switched from off to on. The OS 4000 refers to flag informationstored in the RAM 2006 to make the determination in step S702. In stepS707 described below, the OS 4000 stores information indicating a shiftto the deep sleep mode as the flag information if the mode is shifted tothe deep sleep mode. If the information indicating a shift to the deepsleep mode is stored as the flag information, the OS 4000 determinesthat the MFP 1003 has returned from the deep sleep mode to the normalmode.

If the OS 4000 determines that the MFP 1003 has returned from the deepsleep mode (YES in step S702), the process proceeds to step S709.Otherwise (NO in step S702), the process proceeds to step S703.

In step S703, the network unit control driver 4003 issues an instructionto the network unit 2008 to initialize the network unit 2008.Specifically, the network control unit control driver 4003 sets aregister of the sub CPU 3001 to cancel a reset signal to the sub CPU3001. Further to initialize the MAC/PHY unit 3002, the network controlunit control driver 4003 sets a register of the MAC/PHY unit 3002.Thereby, the network unit 2008 is initialized to become capable ofcommunicating with the main CPU 2001 and the switching hub 1004.

It is assumed that the MAC/PHY unit 3002 of the network unit 2008 andthe switching hub 1004 both support an auto-negotiation function. In theregister of the MAC/PHY unit 3002, whether the auto-negotiation functionis turned on or off can be set. It is assumed that in the register ofthe MAC/PHY unit 3002, as default setting at the time of initializationof the network unit 2008, the auto-negotiation function is turned on. Inthis case, the MAC/PHY unit 3002 transmits a pulse signal called a fastlink pulse (FLP) to the switching hub 1004 in response to theinitialization of the network unit 2008. The FLP is also transmittedfrom the switching hub 1004 to the MAC/PHY unit 3002. The MAC/PHY unit3002 can recognize a communication speed which the switching hub 1004supports based on the FLP received from the switching hub 1004. In suchexemplary embodiments, the MAC/PHY unit 3002 and the switching hub 1004support communication speeds of 10 Mbps, 100 Mbps, and 1000 Mbps. TheMAC/PHY unit 3002 determines 1000 Mbps, that is the highestcommunication speed for both, as a communication speed to be used, andlinks up with the switching hub 1004. The link-up means a communicationlink established state, that is, a data transmission or reception enablestate. Link-down means a non-established state of communication link,that is, a data transmission or reception disable state. Thecommunication link established state means a state where not onlycertain information can be transmitted or received but also packet datacan be transmitted or received.

In step S704, the network unit control driver 4003 transmits a MACaddress that is a physical address allocated to the network unit 2008 tothe switching hub 1004 via the network unit 2008. In step S7003, themain CPU 2001 generates a packet including a MAC address, and performscontrol such that the generated packet is transmitted to the switchinghub 1004 via the MAC/PHY unit 3002 in the network unit 2008. In stepS704, the sub CPU 3001 of the network unit 2008 is not involved in thepacket transmission. In the exemplary embodiment, it is assumed that thenetwork unit control driver 4003 transmits a packet of the AddressResolution Protocol (ARP) including a MAC address to the switching hub1004. Alternatively, the network unit control driver 4003 can transmit apacket of a Gratuitous ARP (GARP) that requests the IP address of thedevice.

If the switching hub 1004 receives the MAC address (in this example00:00:85:00:00:03) of the network unit 2008 from the MFP 1003, theswitching hub 1004 switches a VLAN participation state of the receivedMAC address from “non-participation” to “participation”. The switchinghub 1004 accordingly determines that the computer terminal correspondingto the received MAC address has participated in the VLAN, and managesthe computer terminal.

In step S709, the network unit control driver 4003 issues an instructionto the network unit 2008 to change the register of the MAC/PHY unit 3002of the network unit 2008. Specifically, the setting to turn off theauto-negotiation function in the MAC/PHY unit 3002 is changed to settingto turn it on. In this case, the MAC/PHY unit 3002 transmits a pulsesignal called a FLP to the switching hub 1004 in response to the turningon operation of the auto-negotiation function. The FLP is alsotransmitted from the switching hub 1004 to the MAC/PHY unit 3002. TheMAC/PHY unit 3002 can recognize a communication speed which theswitching hub 1004 supports based on the FLP received from the switchinghub 1004. In this exemplary embodiment, the MAC/PHY unit 3002 and theswitching hub 1004 both support communication speeds of 10 Mbps, 100Mbps, and 1000 Mbps. The MAC/PHY unit 3002 determines 1000 Mbps that isthe highest communication speed for both, to be a communication speed tobe used, and links up with the switching hub 1004.

In step S710, the network unit control driver 4003 transmits a MACaddress that is a physical address allocated to the network unit 2008 tothe switching hub 1004 via the network unit 2008. In step S703, the mainCPU 2001 generates a packet including the MAC address, and performscontrol such that the generated packet is transmitted to the switchinghub 1004 via the MAC/PHY unit 3002 in the network unit 2008. In stepS710, the sub CPU 3001 of the network unit 2008 is not involved in thepacket transmission.

In step S705, the OS 4000 determines whether a sleep shift condition(switching condition) for switching the mode of the MFP 1003 to the deepsleep mode has been established. If the OS 4000 determines that thecondition has been established (YES in step S705), the process proceedsto step S706. If the sleep shift condition has not been established (NOin step S705), the OS 4000 executes step S705 again. The OS 4000determines that the sleep shift condition has been established, forexample, if a state in which neither of the control drivers 4001 to 4006is executed on the OS 4000, continues for a predetermined period (forexample, 15 minutes). For example, if a state where the network unit2008 receives no packet and the operation unit 1010 is not operatedcontinues for a predetermined period, the OS 4000 determines that thesleep shift condition has been established.

In step S706, the network unit control driver 4003 notifies the sub CPU3001 of the network unit 2008 that the MFP 1003 is shifting to the deepsleep mode. In this step, the network unit control driver 4003 notifiesthe sub CPU 3001 of information indicating a speed of communicationcarried out between the network unit 2008 and the switching hub 1004after the shift to the deep sleep mode. In this exemplary embodiment,the network unit control driver 4003 notifies the sub CPU 3001 ofinformation indicating a communication speed of 10 Mbps to set thecommunication speed to the lowest speed.

In the register of the MAC/PHY unit 3002, the setting to turn on theauto-negotiation function has been made. The main CPU 2001 turns off theauto-negotiation. This change is made, in the deep sleep mode, to setthe speed of communication carried out between the network unit 2008 andthe switching hub 1004 to a speed lower than that of the normal mode.

In step S707, the network unit control driver 4003 changes theconnection state between the MAC/PHY unit 3002 and the switching hub1004 from the link-up state where the communication link has beenestablished, to the link-down state where no communication link has beenestablished. Specifically, the network unit control driver 4003 sets theregister of the MAC/PHY unit 3002 to the link-down state. After thisregister setting, the MAC/PHY unit 3002 sets the communication state tothe link-down state.

The switching hub 1004 periodically monitors the link state with the MFP1003, and if the switching hub 1004 detects a link-down state, theswitching hub 1004 switches the VLAN participation state of the MACaddress corresponding to the MFP 1003 from “participation” to“non-participation”. The switching hub 1004 accordingly recognizes thenon-participation state of the MFP 1003 in the VLAN 1 of the switchinghub 1004.

In step S708, the main CPU 2001 transmits a signal for cutting off thepower supply to the power OFF/ON unit 2016 via the control signal line2022. The power OFF/ON unit 2016 that has received the signal cuts offthe power supply to the main components, including the main CPU 2001,via the power supply line 2020. Thus, the MFP 1003 shifts from thenormal mode to the deep sleep mode.

The operation of the MFP 1003 to return from the deep sleep mode to thenormal mode is as described above.

FIG. 8 is a flowchart illustrating an operation performed by the sub CPU3001 of the network unit 2008.

The operation in the flowchart in FIG. 8 is started when the followingprocessing is performed. That is, by changing an operation of the mainswitch (not illustrated) of the MFP 1003 from off to on, power supplystarts from the power supply unit 1009 to the sub CPU 3001. When thenetwork unit control driver 4003 cancels a reset signal of the sub CPU3001, the processing in FIG. 8 starts.

In step S801, the sub CPU 3001 reads a program stored in the ROM 3004 toexpand the program on the RAM 3005, and executes the program expanded onthe RAM 3005. When the program is executed, the network unit 2008 isinitialized, which enables communicating with the main CPU 2001 and theswitching hub 1004.

After the initialization of the network unit 2008, as described above,the MAC/PHY unit 3002 determines the highest communication speed betweenthe MAC/PHY unit 3002 and the switching hub 1004, in this example 1000Mbps, to be the communication speed which is to be used. At thedetermined communication speed, the MAC/PHY unit 3002 links up with theswitching hub 1004.

In step S802, the sub CPU 3001 determines whether the sub CPU 3001 hasreceived a notification of a shift to the deep sleep mode, from thenetwork unit control driver 4003 (main CPU 2001). If the sub CPU 3001determines that the notification has been received (YES in step S802),the process proceeds to step S803. In this step, the sub CPU 3001receives from the main CPU 2001 the notification of the shift to thedeep sleep mode together with the information indicating the speed ofcommunication carried out between the network unit 2008 and theswitching hub 1004 after the shift to the deep sleep mode.

In step S803, the sub CPU 3001 checks whether the network unit controldriver 4003 (main CPU 2001) has set the register of the MAC/PHY unit3002. The sub CPU 3001 accordingly determines whether the MAC/PHY unit3002 and the switching hub 1004 have been set to the link-down state. Ifthe sub CPU 3001 determines that the MAC/PHY unit 3002 and the switchinghub 1004 have been set to the link-down state (YES in step S803), theprocess proceeds to step S804. The register setting of the MAC/PHY unit3002 is changed by the main CPU 2001 to the turn-off of theauto-negotiation function.

In step S804, the sub CPU 3001 switches the connection state between theMAC/PHY unit 3002 and the switching hub 1004 from the link-down state tothe link-up state at the communication speed indicated by thecommunication speed information received from the main CPU 2001 in stepS802. The main CPU 2001 (network unit control driver 4003) has specifiedthe speed of 10 Mbps, that is lower than the communication speed (1000Mbps) in the normal mode, to save power. Consequently, the sub CPU 3001notifies the switching hub 1004 of linking-up at the communication speedof 10 Mbps. According to the notification, the MAC/PHY unit 3002 and theswitching hub 1004 are set to a linked-up state at the communicationspeed of 10 Mbps.

In step S805, the sub CPU 3001 transmits a MAC address that is aphysical address allocated to the network unit 2008 to the switching hub1004 via the MAC/PHY unit 3002. In this exemplary embodiment, the subCPU 3001 transmits the MAC address at intervals of 200 ms in total fourtimes. In other words, in the case where the MFP 1003 has shifted to thesleep mode, the sub CPU 3001 transmits the MAC address (or otheridentification information of the MFP 1003) a plurality of times using afirst method. In step S805, the sub CPU 3001 generates a packetincluding the MAC address, and performs control such that the generatedpacket is transmitted to the switching hub 1004 via the MAC/PHY unit3002. In step S805, the main CPU 2001 is not involved in the packettransmission. The MAC address information is necessary when theswitching hub 1004 causes the MFP 1003 to participate in the VLAN 1.

The MAC address is necessary when the switching hub 1004 causes the MFP1003 to participate in the VLAN 1 due to the reasons described below.When the switching hub 1004 receives the MAC address (for example00:00:85:00:00:03) of the network unit 2008 from the MFP 1003, theswitching hub 1004 switches the VLAN participation state of the receivedMAC address from “non-participation” to “participation”. The switchinghub 1004 accordingly recognizes the participation state of the computerterminal (in this case, the MFP 1003) corresponding to the received MACaddress in the VLAN 1 of the switching hub 1004. However, if a collisionor the like occurs, the packet transmitted to the switching hub 1004 islost, and consequently, the VLAN participation state of the MFP 1003never enters the “participation” state. In another case, depending onthe settings of the switching hub, when a packet is transmitted rightafter linking-up, the determination of VLAN participation may not beperformed. For example, when a communication apparatus transmits apacket almost simultaneously with a linking-up operation and with highfrequency, some switching hubs determine the sender to be a maliciousattacker, and perform control to prevent the participation of theattacker in the VLAN. To solve such problems, in steps S806 and S807,the switching hub 1004 performs again the packet transmission processingfor VLAN participation.

In step S806, the sub CPU 3001 determines whether a predetermined period(such as a few seconds) has passed since the transmission of the packetincluding the MAC address in step S805. The predetermined period is setbased on the time (predetermined time period) until retransmissionprocessing specified by the program read from the ROM 3004. Thepredetermined time can be adjusted depending on the operationenvironment and the installation environment of the MFP 1003, thespecifications of the switching hub which is a communication partner,and the like. If the sub CPU 3001 determines that the predetermined timehas passed (YES in step S806), the process proceeds to step S807. Instep S807, the sub CPU 3001 transmits the MAC address at intervals of100 ms, twice in total. In other words, in the case where the MFP 1003has shifted to the sleep mode, the sub CPU 3001 transmits the MACaddress (or other identification information of the MFP 1003) aplurality of times by a second method.

In this exemplary embodiment, the measurement of the predetermined timeperiod starts after the transmission of the packet including the MACaddress in step S805. Alternatively, the time measurement can be startedafter the linking-up processing in step S804.

In step S808, the sub CPU 3001 determines whether a sleep return factor(whether a return condition has been established) has been detected. Ifthe sub CPU 3001 has detected the sleep return factor (YES in stepS808), the process proceeds to step S809. For example, the following twocases could be the sleep return factors. One is a case where the MAC/PHYunit 3002 has received a WOL pattern via the LAN 1005. The sub CPU 3001determines whether a packet received by the MAC/PHY unit 3002 matches aWOL pattern stored in the ROM 3004. If it matches, it is presumed thatthe sub CPU 3001 has detected a sleep return factor. The other is a casewhere a LAN cable is inserted into or pulled out of a LAN socket of thenetwork unit 2008. The sub CPU 3001 determines whether the LAN cable hasbeen inserted or pulled out. If the sub CPU 3001 determines that the LANcable has been inserted or pulled out, it is presumed that the sub CPU3001 has detected a sleep return factor.

In step S809, the sub CPU 3001 transmits a control signal for resumingthe power supply to the main CPU 2001 and other components to the powerOFF/ON unit 2016 via the control signal line 2023 to start the powersupply to the main CPU 2001.

In step S810, the sub CPU 3001 sets the register of the MAC/PHY unit3002 so that the link-state between the MAC/PHY unit 3002 and theswitching hub 1004 becomes the link-down state. After this registersetting, the MAC/PHY unit 3002 sets the communication state to thelink-down state. The switching hub 1004 periodically monitors the linkstate with the MFP 1003, and if the switching hub 1004 detects alink-down state, the switching hub 1004 switches the VLAN participationstate of the MAC address corresponding to the MFP 1003 from“participation” to “non-participation”. The switching hub 1004accordingly recognizes the non-participation state of the MFP 1003 inthe VLAN 1 of the switching hub 1004.

The first exemplary embodiment has been described above.

According to the first exemplary embodiment, in the deep sleep mode, thecommunication speed between the switching hub and the MFP 1003 isdecreased to the lower speed, and this largely reduces the powerconsumption in the standby state.

Further, according to the first exemplary embodiment, after the shift tothe deep sleep mode (specifically, right after the linking-upoperation), the MAC address is transmitted to the switching hub 1004.Consequently, while the MFP 1003 is operating in the deep sleep mode,the MFP 1003 can participate in the virtual network (MAC address baseddynamic VLAN).

Further, according to the first exemplary embodiment, in the deep sleepmode, the MAC address is retransmitted after the predetermined period oftime has lapsed. This enables the MFP 1003 to surely participate in theVLAN even if a VLAN participation request right after a linking-upoperation failed due to settings of the switching hub, or the like.

In the exemplary embodiment, average power consumption in the operatedstate of the main CPU 2001 is higher than that consumed in the operatedstate of the sub CPU 3001. The main CPU 2001 notifies, during a shift tothe power-saving mode, the network unit 2008 of the shift to the sleepmode and the communication speed; however, the main CPU 2001 is notinvolved in the MAC address transmission. In other words, in the shiftto the power-saving mode, the power supply to the main CPU 2001 is cutoff before a reconnection (linking-up) of the communication link, andconsequently, the communication link is reconnected and the MAC addressare transmitted to the sub CPU 3001. Consequently, as compared with acase where the main CPU 2001 performs the MAC address transmission, thepower consumption can be reduced since the power supply to the main CPU2001 can be cut off at an earlier stage. This also enables power saving.

In the above description, the switching hub 1004 corresponds to the MACbased VLAN, which is a dynamic LAN. Alternatively, other arrangementscan be employed.

For example, the switching hub 1004 can correspond to a subnet basedVLAN that is a dynamic VLAN. In such a case, the switching hub 1004stores a database similar to that illustrated in FIG. 9 as a VLANdatabase in the RAM 5002. The MFP 1003 establishes a communication linkwith the switching hub 1004 to set a link-up state, and then transmits,to the switching hub 1004, an IP address allocated to the MFP 1003 toparticipate in the VLAN 1. After the communication link with the MFP1003 has been established to enter the link-up state, the switching hub1004 receives an IP address (such as 192.168.11.ZZZ) of the MFP 1003. Insuch a case, the switching hub 1004 performs management, presuming thatthe MFP 1003 has (previously) participated in the VLAN 1. The IPaddress, the VLAN number, and the participation state of the VLAN aremanaged in association with each port (from the first port 5004 to thethird port 5006) of the switching hub 1004.

Further, the switching hub 1004 may correspond, for example, to a userbased VLAN that is a dynamic VLAN. In such a case, the switching hub1004 stores a database similar to that illustrated in FIG. 10 as a VLANdatabase in the RAM 5002. The MFP 1003 establishes a communication linkwith the switching hub 1004 to enter link-up state. Then, the MFP 1003transmits, to the switching hub 1004, a user ID (or other userinformation) for identifying a user logging-in the MFP 1003 toparticipate in the VLAN 1. It is assumed that after the communicationlink with the MFP 1003 has been established to enter the link-up state,the switching hub 1004 receives the user ID (such as USER-C) from theMFP 1003. In such a case, the switching hub 1004 performs managementpresuming that the MFP 1003 has participated in the VLAN 1. The user ID,the VLAN number, and the participation state of the VLAN are managed inassociation with each port (from the first port 5004 to the third port5006) of the switching hub 1004.

In the above description, the switching hub 1004 corresponds to thedynamic VLAN (for example, MAC based VLAN). Alternatively, otherarrangements can be employed. For example, a switching hub 1004 thatdoes not correspond to a dynamic VLAN can be employed. The MFP 1003acquires, from the switching hub 1004, information indicating whetherthe switching hub 1004 corresponds to a dynamic VLAN. Based on theacquired information, the MFP 1003 determines whether the switching hub1004 corresponds to a dynamic LAN. If the MFP 1003 determines that theswitching hub 1004 does not correspond to the dynamic LAN, the main CPU2001 does not execute the processing in steps S704 and S710. Further,the sub CPU 3001 also then does not execute the processing in steps S805to S807. Thus, the processing can be appropriately performed dependingon whether the switching hub 1004 corresponds to the dynamic VLAN.

The setting time, for determining whether time to the retransmissionprocessing used in step S806 has lapsed, can be input via an externalinput device such as the operation unit 1010.

In a case where the determination result in step S806 is NO (the settingtime has not lapsed), if a packet is received from a computer terminal(such as PC 1001 or PC 1002) connected via the switching hub 1004, thesub CPU 3001 can determine that the MFP 1003 has participated in theVLAN. In such a case, the processing in steps S806 to S807 may beskipped, and the process can proceed to step S808.

In the exemplary embodiment, in step S807, after the transmission of theMAC address, the process proceeds to step S808. Alternatively, a loopcan execute such that the processing returns to step S806 again todetermine whether a predetermined time has lapsed. In such a case, thetransmission of the MAC address is repeated at predetermined timeintervals. Then, in response to a reception of a packet from a computerterminal (such as PC 1001 or PC 1002) connected via the switching hub1004, the sub CPU 3001 can determine that the MFP 1003 has participatedin the VLAN, and the process can proceed to step S808.

OTHER EMBODIMENTS

Embodiments of the present invention can also be realized by a computerof a system or apparatus that reads out and executes computer executableinstructions recorded on a storage medium (e.g., non-transitorycomputer-readable storage medium) to perform the functions of one ormore of the above-described embodiment(s) of the present invention, andby a method performed by the computer of the system or apparatus by, forexample, reading out and executing the computer executable instructionsfrom the storage medium to perform the functions of one or more of theabove-described embodiment(s). The computer may comprise one or more ofa central processing unit (CPU), micro processing unit (MPU), or othercircuitry, and may include a network of separate computers or separatecomputer processors. The computer executable instructions may beprovided to the computer, for example, from a network or the storagemedium. The storage medium may include, for example, one or more of ahard disk, a random-access memory (RAM), a read only memory (ROM), astorage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures, and functions.

What is claimed is:
 1. A printing apparatus comprising: a printer; and a network interface, wherein, when the printing apparatus shifts from a first power mode in which a communication speed of the printing apparatus is a first speed to a second power mode in which the communication speed of the printing apparatus is a second speed different from the first speed, the network interface transmits identification information of the printing apparatus a plurality of times, wherein, in accordance with a predetermined time period passed after the plurality of times of transmission has completed, the network interface further transmits the identification information a plurality of times.
 2. The printing apparatus according to claim 1, wherein, when the printing apparatus shifts from the first power mode to the second power mode, the network interface transmits the identification information N times, wherein, in accordance with the predetermined time period passed after the N times of transmission has completed, the network interface further transmits the identification information M times, and wherein N is larger than or equal to 3, and M is larger than or equal to 2 and smaller than N.
 3. The printing apparatus according to claim 2, wherein the N times of transmission is performed at intervals of a first time period, and wherein the M times of transmission is performed at intervals of a second time period different from the first time period.
 4. The printing apparatus according to claim 3, wherein the second time period is shorter than the first time period.
 5. The printing apparatus according to claim 3, wherein the first time period is 200 msec, and the second time period is 100 msec.
 6. The printing apparatus according to claim 2, wherein N is 4, and M is
 2. 7. The printing apparatus according to claim 1, wherein the identification information is transmitted to a switching hub.
 8. The printing apparatus according to claim 1, wherein the identification information of the printing apparatus is a MAC address of the printing apparatus.
 9. The printing apparatus according to claim 1, wherein the second power mode is a sleep mode in which power consumption is lower than that in the first power mode, and the second speed is lower than the first speed.
 10. A method for controlling a printing apparatus having a printer and a network interface, the method comprising: when the printing apparatus shifts from a first power mode in which a communication speed of the printing apparatus is a first speed to a second power mode in which the communication speed of the printing apparatus is a second speed different from the first speed, the network interface transmits identification information of the printing apparatus a first plurality of times; and in accordance with a predetermined time period passed after the first plurality of times of transmission has completed, the network interface further transmits the identification information a second plurality of times. 